I have an ancient (and awesome*) Creative Zen Xtra that uses a 5v - 1.5a charger... Plugs looked identical to my roommates PSP charger. After a snifter o wine I took the plunge... Instantly saw the little lightning bolt next to the battery meter. Yay, one less thing to buy and carry!
I'm thinking the charging in-port on the 505 is a lot more common than most gizmos. Knowing Sony, if this gets out... they'll make a proprietary one that is backasswards.
Here's a
Sony PSP charger on Amazon marketplace for .72 + 2.98 shipping = $3.70 total.. the reviews are decent.
*While huge, the Zen Xtra has a user a very easily replaceable, cheap 2.5" hard drive. I've put about 7 hard drives in the thing (most warranty replacements).... I shudder to think how much replacement ipods would have cost.